Big block conversions

I need to know what it would take to put a 454 big block into my '78 1 ton which is now fitted with a 305 small block. Would I need new engine mounts? Will I need a new bell housing? Please help

The 454 should bolt right up to your bell housing and the mounts should also line up and work, however you may not have enough radiator to keep the 454 cool enough and the smaller transmission may not hold up to the abuse you can dish it with the 454. You should change the transmission to a 400 at the same time. This will however require some driveline modifiations. If you will be using this vehicle for light duty use the 350 tranny should hold up fine. Good Luck.